The overall objective of this proposed research is to further characterize the mechanisms of production, and the possible influences on cell function, of two structural variants of the specific IL-1 receptor antagonist (IL-1ra)found inside cells. The first form of this molecule, termed secretory or slL-1ra, is a major extracellular product of monocytes, macrophages and neutrophils. The second form is iclL-1ra, an intracellular molecule found in keratinocytes and other epithelial cells. We have now determined that iclL-1ra is also a major product of synovial fibroblasts and is synthesized in a delayed fashion by monocytes and macrophages. In recent studies, we have observed that a 16kD low molecular weight form of IL-1ra is present in considerable amounts in monocytes, macrophage cell lines and neutrophils. The terminology for this unique family of molecules has been expanded to: slL-1ra, iclL- 1ra(1)(the original cytosolic form), and iclL-1ra(2) (the new low molecular weight cytosolic form). The hypothesis to be examined is that the production of two intracellular forms of IL-1ra by human monocytes, macrophages, fibroblasts and keratinocytes, may involve unique transcriptional or transnational mechanisms in comparison to slL-1ra production by mononuclear phagocytes or fibroblasts. The presence of iclL-1ra(1) or iclL-1ra(2) inside cells may influence the regulation of lL-1 receptor expression or particular lL-1-induced biological responses. Three specific aims will be addressed in these studies: 1) To determine the mechanisms of regulation of production of iclL-1ra(1). 2) To determine mechanisms of regulation of production of iclL-1ra(2). 3) To determine the influence of structural variants of lL-1ra found inside cells on regulation of lL-1 receptor expression or on specific lL-1 induced biological responses. These studies will utilize the techniques of polymerase chain reaction and primers for lL-1ra, specific ELISA, transfection, morphological approaches, and equilibrium binding. These studies are related to human joint and skin diseases where inflammatory effects of lL-1 are important in pathophysiology. L-1ra may not only inhibit binding of lL-1 to extracellular receptors, but the intracellular structural variants of this molecule may decrease lL-1 effects through influencing receptor expression or initiation of signals. The proposed studies will further determine the mechanisms of production to specific functions of the cell. A greater understanding of the physiology and effects of lL-1ra should result in unique and novel ways to approach the treatment of patients with acute and chronic arthritis or skin diseases.